KR100940238B1 - Electrophotographic toner and electrophotographic image forming apparatus employing the same - Google Patents

Abstract

An electrophotographic toner and an electrophotographic image forming apparatus employing the same are disclosed. The disclosed electrophotographic toner includes toner base particles comprising a binder resin, a colorant, a release agent, and a charge control agent; And a primary average particle diameter of 50 to 150 nm, preferably 80 to 130 nm, an average shape coefficient (SF1) of 100 to 120, a shape factor of 0.96 to 1, and an aspect ratio of 0.89 to 1 And a barium titanate external additive added to the surface of the toner base particles.

Accordingly, the disclosed electrophotographic toner has high charging stability and high image density and excellent transfer efficiency even when printed for a long time, and the external additive has an effect that the external additive does not detach from the surface of the toner base particles.

Description

Electrophotographic toner and electrophotographic image forming apparatus employing the same

The present invention relates to an electrophotographic toner and an electrophotographic image forming apparatus employing the same. More particularly, the charging stability is high, so that even when printing for a long time, the image density is high and the transfer efficiency is excellent. The present invention relates to an electrophotographic toner in which no external additive is detached and an electrophotographic image forming apparatus employing the same.

In general, an electrophotographic image forming apparatus includes a developing device including a toner cartridge and a photosensitive member, a transfer unit, and forms an electrostatic latent image by scanning light onto the photosensitive member charged at a constant electric potential, and the electrostatic latent image It refers to an apparatus for forming a visible image by transferring and fixing the developed toner image to a print medium after development with a toner). Such a device includes a laser printer, a facsimile machine, a copier, and the like.

Dry toner can be divided into one-component toner and two-component toner according to the charging method of the toner particles, and can be divided into magnetic and nonmagnetic by means of moving the charged toner particles to the latent image portion on which the electrostatic latent image is formed. The one-component toner refers to a toner which causes charging through friction between toner particles or friction between the toner and the doctor blade, and the two-component toner charges through friction with a carrier by mixing nonmagnetic toner particles and magnetic carrier particles. Means toner. In addition, the nonmagnetic toner refers to a toner that is moved by the fluidity of the toner particles themselves without using a magnetic force. The magnetic toner refers to a toner that is moved by using a magnetic force by mixing magnetic materials such as ferrite in the toner.

The operation of the non-contact developing electrophotographic image forming apparatus 4 using the nonmagnetic one-component toner will be described with reference to FIG.

A charging bias voltage is applied to the charging roller 2 in order to charge the outer circumference of the photosensitive member 1 to a uniform electric potential.

The exposure signal 3 is light corresponding to image information of each color such as cyan, magenta, yellow, and black, and the photosensitive member according to an electrical signal. It is investigated in (1).

The toner 8 is supplied to the developing roller 5 by a supply roller 6 composed of elastic members such as polyurethane foam and sponge.

The toner 8 supplied to the developing roller 5 reaches the contact portion of the toner doctor blade 7 and the developing roller 5 as the developing roller 5 is rotated. Here, the toner doctor blade 7 is made of an elastic member such as metal or rubber. The toner 8 is regulated to a predetermined thickness by passing between the contact portion of the toner doctor blade 7 and the developing roller 5 and is thinned, and the toner 8 is sufficiently charged in this process. The thinner toner 8 is transferred to the developing region where the electrostatic latent image of the photosensitive member 1 is formed by the developing roller 5.

The developing roller 5 is disposed to face the photosensitive member 1 at a predetermined interval. The developing roller 5 rotates counterclockwise and the photosensitive member 1 rotates clockwise.

The toner 8 transferred to the developing region of the photosensitive member 1 is formed by the electric force generated by the potential difference between the voltage applied from the power supply 12 to the developing roller 5 and the latent potential of the photosensitive member 1. The latent electrostatic image formed on the upper side is developed to form a toner image.

The toner image formed on the photosensitive member 1 reaches the position of the transfer unit 9 according to the rotational direction of the photosensitive member 1. A transfer bias voltage of opposite polarity to that of the toner image is applied to the transfer unit 9 so that the toner image developed on the photosensitive member 1 is transferred to the print medium 13. The toner image is transferred to the print medium 13 by the electrostatic force acting between the photosensitive member 1 and the transfer unit 9.

The toner image transferred to the print medium 13 is fixed on the print medium while passing through a high temperature and high pressure fuser (not shown). On the other hand, the remaining toner 8 'remaining on the outer circumferential surface of the photoconductor 1 after the transfer is removed by the cleaning blade 10.

Generally, the toner is composed of toner base particles, external additives, and other additives, and the toner base particles include a binder resin, a colorant, a charge control agent, and a release agent, and the external additive is added to the surface of the toner base particles.

In the color image forming apparatus, toners of four colors such as yellow (Y: yellow), magenta (M: magenta), cyan (C: cyan), and black (K: black) are typically used. Therefore, in the case of a color image forming apparatus, at least four different colorants must be used to realize each toner color.

Toner base particles are generally produced by kneading pulverization, suspension polymerization, emulsion polymerization, or the like.

The toner finished product is manufactured by blending or adding particulate external additives such as silica, metal oxide, and / or organic matter to the surface of the toner base particles thus prepared.

Toner particles develop an electrostatic latent image of the photosensitive member 1 by frictional charging as described above to form a toner image, and retain positive or negative charging according to the polarity of the developed electrostatic latent image. At this time, the charging performance of the toner is also affected by the blending of the toner base particles, but mainly due to the external additive added to the surface of the toner base particles. Can be adjusted.

On the other hand, even when the external additive is uniformly coated on the surface of the toner base particles, as the printing proceeds, agglomeration between the toner particles occurs due to the pressure applied to the toner, or agglomerates to the toner doctor blade or the sleeve (developing roller). In this case, the image becomes blurred and uneven in the long term. In order to solve this problem, the selection of an appropriate external additive and the design of its content and particle size are very important.

Various methods for solving this problem have been proposed as follows.

Japanese Patent Laid-Open No. 1991-100661 discloses two types of inorganic fine particles having different average particle diameters, that is, particles having an average particle diameter of 5 nm or more and less than 20 nm and an average particle diameter of 20 nm or more and 40 nm in order to improve the developability, transferability, and cleaning properties of the toner. It is disclosed that a specific amount is added in combination with the following particles. In the initial stages, high developability, transferability and cleaning property can be obtained, but since the stress applied to the toner cannot be reduced over time, the external additives are easily buried or detached, and thus developability and transferability can be achieved. This is a significant change from the initial stage.

On the other hand, Japanese Laid-Open Patent Publication No. 1995-028276 discloses that it is effective to use inorganic fine particles having a large particle size in order to suppress the embedding of external additives in a toner phase. However, since the inorganic fine particles have a specific gravity, desorption of the external additives due to stirring stress cannot be avoided when the size of the external additives is increased. In addition, since the inorganic fine particles do not have a perfect spherical shape, it is difficult because the standing of external additives cannot be controlled constantly when they are deposited on the toner surface.

Korean Patent Laid-Open Publication No. 2006-0083898 includes a primary coating layer and a secondary coating layer formed on the surface of a toner particle, wherein the primary coating layer contains a coating organic powder in which two organic powders are coated on each other's surface. The secondary coating layer discloses a method for producing a nonmagnetic one-component toner containing a coated inorganic powder in which silica and titanium dioxide are coated on each other's surface.

Japanese Laid-Open Patent Publication No. 1998-288855 discloses a toner base particle containing a colorant and a binder resin, and a toner using an inorganic fine powder having a porosity of 10.0 to 50.0% as an external additive.

Korean Laid-Open Patent Publication No. 2002-0061683 discloses a method of manufacturing a toner that controls the distribution of the charge control agent on the surface of the toner particles to secure a uniform charging state between the toner particles, and improves the charging stability to establish long-term reliability of the toner. have.

With the recent rapid development of digital devices, high quality, high speed, and colorization are rapidly progressing, so that a toner having a more accurate and efficient transfer performance and a stable charging performance in the long term is still required.

In order to solve the problems of the prior art as described above, the present invention is excellent in long-term charging stability, even if printing for a long time, the image density is maintained high and the transfer efficiency is excellent, and the external additives are not detached to prevent contamination in the developing apparatus. It is to provide an electrophotographic toner.

Still another object of the present invention is to provide an electrophotographic image forming apparatus employing the toner.

The present invention to solve the above problems,

Toner base particles comprising a binder resin, a colorant, a release agent, and a charge control agent; And

The primary mean particle size is 50 to 150 nm, preferably 80 to 130 nm, the average shape coefficient (SF1) is 100 to 120, the shape factor is 0.96 to 1, and the aspect ratio is 0.89 to 1. And a barium titanate external additive added to the surface of the toner base particles.

According to one embodiment of the invention, the external additive may be included in a ratio of 0.3 to 5 parts by weight, preferably 1 to 3 parts by weight with respect to 100 parts by weight of the toner base particles.

According to another embodiment of the present invention, the toner base particles have an average aspect ratio of 0.975 to 1 and a volume average particle diameter of 5 to 7 μm.

According to another embodiment of the present invention, the electrophotographic toner has a primary average particle diameter of 5 to 50 nm, preferably 5 nm to 30 nm, and surface treated with hexamethyldisilazane (HMDS) (hereinafter, Additional external additive A); And silica (hereinafter referred to as additional external additive B) having a primary average particle diameter of 30 to 80 nm and surface treated with polydimethylsiloxane (PDMS) as an external additive.

According to another embodiment of the present invention, the electrophotographic toner is an inorganic compound having a primary average particle diameter of 10 to 100 nm, preferably 50 nm to 90 nm (hereinafter referred to as additional external additive C); As further included.

According to another embodiment of the present invention, the electrophotographic toner includes 1 to 16 parts by weight of an external additive as a whole with respect to 100 parts by weight of the toner base particles. More specifically, the additional external additive A, in addition to the barium titanate external additive, is contained in an amount of 0.5 to 5 parts by weight based on 100 parts by weight of the toner base particles; Additional external additive B is 0.1 to 3 parts by weight; The additional external additive C may be included in a ratio of 0.1 to 3 parts by weight.

Also according to the invention,

An electrophotographic image forming apparatus employing an electrophotographic toner according to any one of the above embodiments is provided.

According to the present invention, an electrophotographic toner that can not only be excellent in image density and charging stability but also improve long-term stability and realize high quality images can be provided.

In addition, according to the present invention, an electrophotographic toner can be provided which maintains excellent charging characteristics, can maintain high quality over a long period without degrading developability and transferability, and can prevent contamination in a developing apparatus. .

In addition, according to the present invention, an electrophotographic image forming apparatus employing the toner can be provided.

Hereinafter, the present invention will be described in more detail.

The electrophotographic toner according to one embodiment of the present invention includes toner base particles and an external additive.

The toner base particles may include a binder resin, a colorant, a release agent, a charge control agent, and the like.

The binder resin is included in the toner base particles to hold other components of the toner, such as a colorant, a charge control agent, and / or a releasing agent, and / or an external additive described below, and serve as a binder or fixing agent for fixing the toner to a print medium. Do this. As the binder resin, various known resins may be used, for example, polystyrene, poly-P-chlorostyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene air Copolymer, Styrene-vinylnaphthalene copolymer, Styrene-methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, Styrene-propyl acrylate copolymer, Styrene-butyl acrylate copolymer, Styrene-octyl acrylate copolymer, Styrene-methyl methacrylate Copolymer, styrene-ethyl methacrylate copolymer, styrene-methacrylate propyl copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethacrylate copolymer, styrene-acrylonitrile copolymer, Styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl ethyl ketone copolymer, styrene-butadiene ball Styrene-based copolymers such as polymers, styrene-acrylonitrile-indene copolymers, styrene-maleic acid copolymers, styrene-maleic acid esters, polymethyl methacrylates, polyethyl methacrylates, polybutyl methacrylates, and air Copolymer, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin , Aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like may be used alone or in combination. Of these, polyester resins are excellent in fixing properties and transparency, and are suitable for color toners.

The colorant is for causing the toner to exhibit color. Currently, electrophotographic toners include toners including black (K), yellow (Y: yellow), magenta (M: magenta), and cyan (C: cyan) colorants. The toners may be employed in an electrophotographic image forming apparatus. Among these image forming apparatuses, an image forming apparatus employing only a toner including a black colorant is called a black and white chemical forming apparatus, and each of the four toners includes four colors. An image forming apparatus employing all kinds of toners is called a color image forming apparatus.

Although not limited to this, as the black colorant, iron oxide, carbon black, titanium oxide and the like are used.

As a yellow coloring agent, a condensed nitrogen compound, an isoindolinone compound, an atlakin compound, an azo metal complex, an allyl imide compound, etc. are used, for example. Specifically C.I. Pigment Yellow 12, 13, 14, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168 or the like can be used.

Examples of magenta colorants include condensed nitrogen compounds, anthraquines, quinacridone compounds, base dye rate compounds, naphthol compounds, benzo imidazole compounds, thioindigo compounds, or perylene compounds. Specifically C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221, or 254 may be used.

As a cyan colorant, the copper phthalocyanine compound, its derivative (s), anthrakin compound, a base dye rate compound, etc. are used, for example. Specifically C.I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 or the like can be used.

Such colorants may be used alone or as a mixture of two or more of the toners of each color as described above. The mixing and mixing ratio of the colorants should be determined in consideration of color, saturation, lightness, weather resistance, dispersibility in toner, and the like.

The content of the colorant may be sufficient to color the toner to form a visible image by development. For example, 2 to 20 parts by weight is preferable based on 100 parts by weight of the binder resin. If the content is less than 2 parts by weight, the coloring effect is insufficient. If the content is more than 20 parts by weight, the electric resistance of the toner is lowered, so that a sufficient amount of triboelectric charge cannot be obtained, which is undesirable.

As the charge control agent, both an antistatic charge control agent and an antistatic charge control agent may be used. Examples of the antistatic charge control agent include organic metal complexes or chelate compounds such as chromium-containing azo dyes or monoazo metal complexes; Metal containing salicylic acid compounds such as chromium, iron and zinc; And organometallic complexes of aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids may be used, and any known ones are not particularly limited. In addition, examples of the positive charge control agent include quaternary ammonium salts such as products modified with nigrosine and fatty acid metal salts thereof, tributylbenzyl ammonium 1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate. An onium salt etc. can be used individually or in mixture of 2 or more types. Such a charge control agent charges the toner stably and at high speed by the electrostatic force, thereby stably supporting the toner on the developing roller.

The content of the charge control agent contained in the toner is generally within the range of 0.1 parts by weight to 10 parts by weight with respect to 100 parts by weight of the entire toner.

The toner base particles according to the present embodiment may include a release agent capable of improving fixability of the toner image. Release agents include polyalkylene waxes such as low molecular weight polypropylene and low molecular weight polyethylene, ester waxes, carnauba waxes, paraffin waxes, montan waxes, rice waxes, candelilla waxes ) May be used.

In addition, the toner base particles may further include higher fatty acids or fatty acid amides or the like or metal salts thereof in order to protect the photoconductor and prevent deterioration of developing characteristics to obtain a high quality image.

It is preferable that the toner base particles thus prepared have an average aspect ratio of 0.975 to 1.0. More preferably, the average aspect ratio is 0.980 to 1.0. When the average aspect ratio is 1.0, the shape of the toner base particles is a perfect spherical shape, and the lower the value, the farther from the sphere, the surface area thereof increases, and the surface area of the toner base particles increases, thereby increasing the electrostatic adhesion force, thereby drastically lowering the transfer efficiency.

In addition, the smaller the average aspect ratio of the toner base particles, the more the external additives described later are buried on the surface of the toner base particles and do not adhere uniformly. Substantially, when the average aspect ratio is less than 0.975, the function of the external additive , Role of spacer, imparting fluidity, etc.) are lowered.

The aspect ratio can be calculated by the following Equation 1 by measuring 100 random toner base particle samples with an SEM image (x 1,500) and analyzing the image with Image J software.

[Equation 1]

1 / aspect ratio = maximum length of the particle / maximum length perpendicular to the maximum length of the particle

The aspect ratio may have a value of 0 to 1, and the closer to 1, the closer to the sphere.

Further, in the embodiment of the present invention, the volume average particle diameter of the toner base particles is 5 to 7 mu m, preferably 5.5 to 6.5 mu m. If the volume average particle diameter is less than 5 mu m, the surface area of the toner base particles is large, the electrostatic adhesion force is increased, and the transfer efficiency is drastically reduced, which is not preferable. In addition, when the volume average particle diameter exceeds 7 µm, scattering of the toner occurs in the developing process and the transferring process, which reduces the reproducibility of the electrostatic latent image, which makes it difficult to obtain high image quality. In addition, setting the volume average particle diameter of the toner base particles in the above range is also preferable for color reproducibility in a full color image. However, as the resolution of the printed image increases, the volume average particle size of the toner base particles should be reduced, and the particle size can be variously adjusted according to various manufacturing methods, and thus the protection scope of the present invention is not limited by the particle size range. .

In the present invention, the toner base particles are not limited to a special manufacturing method but can be produced by a known method. As a manufacturing method of a toner base particle, For example, melt-kneading milling method of melt-kneading, grinding | pulverizing, and classifying a binder resin, a coloring agent, a mold release agent, a charge control agent, etc .; A method of changing the shape by applying mechanical impact or thermal energy to the particles obtained by melt kneading grinding; Emulsion polymerization agglomeration method for emulsion polymerizing a polymerizable monomer of a binder resin, mixing a formed dispersion with a dispersion such as a colorant, a mold releasing agent, a charge control agent, and coagulating and heat fusion to obtain toner base particles; A suspension polymerization method in which a polymerizable monomer for obtaining a binder resin and a mixed solution such as a colorant, a mold release agent, a charge control agent and the like are suspended in an aqueous solvent and polymerized; A dissolution suspension method in which a mixed solution of a binder resin, a colorant, a mold release agent, a charge control agent and the like is suspended and granulated in an aqueous solvent; Etc. can be mentioned.

The toner base particles obtained by the above method are used as cores, and particles of monomers or binder resins are agglomerated and agglomerated, and the toner base particles having a core-shell structure can be produced by heat fusing and attaching the aggregated particles. .

The external additive is added to the surface of the toner base particles to give the toner fluidity, charge stability, and cleaning properties and other properties required for the toner. In the present invention, the temperature of the toner charge amount and / or the barium titanate is used as the external additive. Alternatively, it is possible to control the charge amount by reducing the humidity dependence, not to change the fluidity, and to control the stirring efficiency in the developing device constantly, thereby keeping the charge amount of each toner uniform, The effect was to improve the pollution in the interior. In addition, it was possible to maintain the transfer performance at the same or similar level as the initial stage, to stably maintain high quality over a long period of time, and to obtain the effect of satisfying charging stability.

In addition, the barium titanate external additive may have an average shape coefficient (SF1) of 100 to 120, a shape factor of 0.96 to 1, and an aspect ratio of 0.89 to 1. If the average shape factor SF1, shape factor, and aspect ratio are out of this range, the barium titanate external additive will affect the original shape of the toner base particles when attached to the toner base particles. It may cause contamination inside the apparatus or contamination and damage to the charging roller.

Aspect ratio can be obtained by Equation 1 by measuring the SEM image (x100,000) of 100 external additive particles at random, and then analyzing it with Image J Software.

The shape coefficient can be obtained by Equation 2 by measuring SEM image (x100,000) of 100 external additive particles at random and analyzing the image by Image J Software.

[Equation 2]

Shape factor = 4π (area / perimeter ^ 2)

In the above formula, the area represents the projection area of the external additive particles, and the perimeter represents the circumferential length of the projection image of the external additive particles. The shape coefficient is a value of 0 to 1, and the closer to 1, the spherical shape.

The average shape coefficient (SF1) can be obtained by Equation 3 below by measuring SEM image (x100,000) of 100 external additive particles at random and analyzing the image by Image J Software.

[Equation 3]

Mean shape factor (SF1) = (absolute maximum diameter of diameter) ² / Projection Area x (π / 4) x100

SF1 having a value between 100 and 120 is close to a spherical particle, and having a value between 140 and 150 has a non-spherical shape.

On the other hand, the toner base particles and the external additives may be mixed with a Henschel mixer, a V mixer, a cyclo mixer, or the like to prepare a toner finished product having an external additive.

Figure 2a is a diagram showing the distribution of the external additives attached to the surface of the toner base particles when only a spherical external additive is used, Figure 2b is attached to the surface of the toner base particles when a mixture of spherical external additives and non-spherical external additives are used Showing the distribution of external additives.

Referring to FIG. 2A, a spherical large particle external additive 31 and a spherical small particle external additive 32 are attached to the surface of the toner base particles 20. When the toner base particles 20 to which the external additives 30 are attached are shaken and agitated, although the large particle external additives 31 are partially buried on the surface of the toner base particles 20, the entire toner base particles 20 may be formed. Not only does the shape change significantly, but the shape of the external additive 30 also maintains its original shape before stirring, and the external additives 31 and 32 are uniformly distributed on the surface of the toner base particles 20.

On the other hand, referring to FIG. 2B, the external additive 30 is a spherical large particle external additive 31, a spherical small particle external additive 32, and a non-spherical (hexahedral) large particle external additive 33. Consists of. When the toner base particles 20 to which the external additives 30 are attached are shaken and agitated, the spherical large particle external additives 31 are partially buried on the surface of the toner base particles 20 to maintain an overall shape, but are non-spherical. The large-diameter external additive 33 is not only difficult to maintain a round shape by embedding a substantial portion on the surface of the toner base particles, but also changes the overall shape of the toner base particles 20. In addition, each of the external additives 31, 32, 33 is not evenly distributed on the surface of the toner base particles 20.

It is preferable that the said barium titanate external additive has a primary average particle diameter of 50-150 nm. If the primary average particle diameter is less than 50 nm, the barium titanate external additive may get stuck on the surface of the toner particles, which may adversely affect charging or fluidity. If the primary average particle diameter exceeds 50 nm, the barium titanate external additive may be toner. It is undesirable because the phenomenon of collision with each other on the surface of the particles may occur and cause contamination.

The amount of the barium titanate external additive added is preferably 0.3 to 5 parts by weight, more preferably 1 to 3 parts by weight based on 100 parts by weight of the toner base particles. If the added amount of the external additive is less than 0.3 part by weight, it is not preferable because the charging stability is not satisfied. If the amount of the external additive is more than 5 parts by weight, it becomes an excessive coating state and causes a secondary obstacle described later by contact of the excess inorganic compound.

The external additive may be used in combination of two or more kinds of external additives having different primary average particle diameters in order to prevent external additive separation from the surface of the toner base particles, which causes image deterioration, or to prevent external additives from buried in the surface of the toner base particles. In addition, these external additives may be used for hexamethyldisilazane (HMDS) and / or polydimethylsiloxane (PDMS) for the effects of toner fluidity and preservation, enhancement of triboelectric chargeability, control of mixing properties, and improvement of developability and transfer stability. Surface-treated with a surface treating agent).

For example, in this example, the external additive may be silica (additional external additive A) having a primary average particle diameter of 5 to 50 nm and surface treated with hexamethyldisilazane (HMDS); And silica having a primary average particle diameter of 30 to 80 nm and surface treated with polydimethylsiloxane (PDMS) (additional external additive B). However, the present invention is not limited thereto, and the external additive may include any known large particle silica and small particle silica in place of the additional external additives A and B. In addition, the external additive may further include an inorganic compound (additional external additive C) having a primary average particle diameter of 10 to 100 nm. Here, the external additive having a relatively large particle size is a spacer particle, and serves to prevent deterioration of the toner and improve charging stability, and the external additive having a relatively small particle size mainly serves to impart fluidity to the toner. .

The primary average particle diameter of the external additive was measured by using a laser diffraction / scattering particle distribution measuring device (Malvern 2000).

If the first average particle diameter of the additional external additive A used in this embodiment is less than 5 nm, it is difficult to manufacture and the price is high, and the phenomenon of the additional external additive A getting stuck on the surface of the toner particles occurs, which adversely affects charging or fluidity. Therefore, it is not preferable, and when the primary average particle diameter exceeds 50 nm, not only the non-electrostatic adhesion force is reduced but also the detachment of the external additive becomes easy, which is not preferable because it causes secondary disturbances such as charging inhibition and image quality defects. More preferably, the additional external additive A is monodisperse spherical silica having a primary average particle diameter of 5 nm to 30 nm.

Specific examples of the additional external additive A, which is silica treated with hexamethyldisilazane (HMDS), include RX300, RX812, R812S, RX200, RX8200, NX90, NAX50, RX50 (above, Japan Aerosil Corporation), TG810G (Cabot) Products).

The addition amount of the additional external additive A is preferably 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight based on 100 parts by weight of the toner base particles. If the added amount is less than 0.5 parts by weight, it is not preferable because the non-electrostatic adhesion is insufficient, the development and transfer improvement effect cannot be sufficiently obtained, and if it is more than 5 parts by weight, it is beyond the amount capable of covering the surface of the toner base particles monolayer. It is undesirably easy to cause excessive interference with the toner base particles and cause secondary disturbances such as charge inhibition and image quality defects.

The additional external additive A is uniformly dispersed in the toner base particles. In addition, the additional external additive A can control the fluidity and chargeability of the toner and sufficiently cover the surface of the toner base particles, but can not effectively express the spacer effect. It is preferable to use together.

The additional external additive B used in this embodiment is added to the surface of the toner to obtain effects such as enhancement of triboelectric chargeability of the toner, adjustment of mixing properties, improvement of developability, improvement of image density, and transfer stability.

The additional external additive B can impart a high tribological electrical charge to the toner when used together with the additional external additive C and barium titanate. Specific examples of the additional external additive B include RY50, NY50, RY200, RY200S, and R202 (above, manufactured by Aerosil Japan).

More preferably, the additional external additive B has a primary average particle diameter of 40 to 60 nm. Although the first average particle diameter of the additional external additive B used in the present embodiment is less than 30 nm, it is expensive, but the additional external additive B is stuck to the surface of the toner particles, which is not preferable because it adversely affects charging or fluidity. In addition, if the primary average particle diameter exceeds 80 nm, it is not preferable because the advantage of adhesion of the toner surface due to the size is lost, which adversely affects charging and the like.

The addition amount of the additional external additive B is preferably 0.1 to 3 parts by weight, more preferably 0.3 to 2 parts by weight based on 100 parts by weight of the toner base particles. If the added amount is less than 0.1 part by weight, the non-electrostatic adhesion is insufficient, and if it exceeds 3 parts by weight, the toner base particles are excessively coated beyond the amount capable of monolithically covering the surface of the toner base particles, thereby inhibiting charge, It is not preferable to easily cause secondary disturbances such as image quality defects.

Examples of the inorganic compound that can be used as the additional external additive C include silica, titanium compounds, alumina, calcium carbonate, magnesium carbonate, calcium phosphate, cesium oxide, barium oxide compounds, and the like. In addition, according to the intended use, the surface of the additional external additive C can be subjected to a known surface treatment.

The additional external additive C is for facilitating charge control. As the additional external additive C, a titanium compound is preferably used in view of suppressing the temperature and / or humidity dependency of the toner charging amount. When using a titanium compound as additional external additive C, it is preferable to process the surface with strontium.

More preferably, the additional external additive C has a primary average particle diameter of 50 to 90 nm. More preferably, the additional external additive B has a primary average particle diameter of 40 to 60 nm. If the first average particle diameter of the additional external additive C used in the present example is less than 10 nm, it is expensive, and since it is not externally harmonized with other external additives, contamination occurs, and thus, the first average particle diameter exceeds 100 nm. If the particle size or particle shape causes contamination after external attachment or adversely affects charging, it is not preferable.

The addition amount of the additional external additive C is preferably 0.1 to 3 parts by weight, more preferably 0.3 to 1 part by weight based on 100 parts by weight of the toner base particles. If the added amount is less than 0.3 part by weight, charging control is not easy, and if it is more than 5 parts by weight, an excessive coating state is caused, and the above-described secondary disorder is liable to be caused due to contact of the excess inorganic compound. not.

In addition to the external additive, other various additives may be added as necessary. Such additives include, for example, fluidizing agents; Cleaning aids such as polystyrene fine particles, polymethyl methacrylate fine particles, and polyvinylidene fluoride fine particles; Or a transcription aid.

Hereinafter, the manufacturing process of the electrophotographic toner according to the present embodiment will be described in detail.

First, the melt kneading grinding method will be described.

In the above method, first, the colorant is treated to be uniformly dispersed in the binder resin. To this end, the colorant may be previously flushed or melt kneaded with the binder resin in high concentration using a master batch. For example, the binder resin and the colorant may be mixed by kneading means such as two rolls, three rolls, pressure kneaders, or a twin screw extruder. The mixture of the binder resin and the colorant is melt kneaded at a temperature of 80 to 180 ° C. for 10 minutes to 2 hours. Subsequently, the mixture is pulverized by a mill such as a jet mill, a friction mill, or a rotary mill, and toner base particles having a volume average particle diameter of 7 to 9 탆 are produced through classification. By adding an external additive to such toner base particles, powder fluidity, charging stability, and the like are improved.

Next, an emulsion polymerization flocculation method is demonstrated.

First, an emulsion of a binder resin, a colorant, a mold release agent, and the like is prepared, and then polymerized to form a toner component having a particle size of less than 1 μm, followed by agglomeration, and primary aggregation from 1 μm to 3 μm. Then, toner particles having a size of 5 µm to 10 µm are prepared by secondary aggregation by adding latexes having different molecular weights.

In addition, in order to attach the external additives to the toner base particles, the toner base particles and the external additives are blended in a predetermined ratio, and then filled and stirred in a stirring apparatus such as a Henschel mixer and stirred toner base particles. A method of adhering an external additive to the surface of the toner, and a method of filling and agitating both particles in a surface reformer such as a 'nara hybridizer' so that at least a portion of the external additive particles are buried on the surface of the toner particles may be used. Can be.

The electrophotographic toner according to the present invention can be equally applied to a contact nonmagnetic one-component toner in addition to the noncontact nonmagnetic one-component toner as described above. Here, the contact type refers to a method in which an electrostatic latent image is developed with toner by contact between the developing roller and the surface of the photoconductor, and the non-contact type means that the developing roller and the surface of the photoconductor are spaced at a predetermined interval, and the toner is applied to the developing roller and the photosensitive member. It means that the developed and moved by the electric force generated according to the potential difference of the latent potential of the.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example

Examples 1-1 to 1-15 and Comparative Examples 1-1 to 1-8

(Preparation of cyan toner base particles)

Polyester resin (molecular weight: 2.5 × 10 ⁴ ) 92 parts by weight (460 g), phthalocyanine pigment blue 15: 3 5 parts by weight (25 g), quaternary ammonium salt 1 part by weight (5 g), low molecular weight polypropylene 2 parts by weight (10 g) Was mixed with a Henschel mixer. This mixture was melt-kneaded at a temperature of 165 ° C. in a twin-screw melt kneader, finely pulverized with a jet mill grinder, and then classified in a wind classifier to obtain toner base particles having a volume average particle diameter of 7.0 μm.

(External process)

The toners of the respective examples and comparative examples were prepared by treating the untreated toner base particles prepared by the melt kneading pulverization method with the external additives as shown in Table 1, respectively, in the compositions shown in Table 2. The external treatment was performed by adding each external additive of Table 1 to the toner base particles (based on 100 parts by weight of the toner base particles) and mixing for 3 minutes with a Henschel type mixer.

External additive type characteristic Display Barium titanate SF1 is 115, shape factor is 0.98, aspect ratio is 0.95, and primary average particle diameter is 100 nm 100nm Ba-1 SF1 is 130, shape factor is 0.98, aspect ratio is 0.95, and primary average particle diameter is 100 nm 100nm Ba-2 SF1 is 115, shape factor is 0.90, aspect ratio is 0.95, and primary average particle diameter is 100nm 100nm Ba-3 SF1 is 115, shape factor is 0.98, aspect ratio is 0.80, and primary average particle diameter is 100nm 100nm Ba-4 SF1 is 115, shape factor is 0.98, aspect ratio is 0.80, and primary average particle diameter is 40nm 40nm Ba-5 SF1 is 115, shape factor is 0.98, aspect ratio is 0.80, and primary average particle size is 160nm 160nm Ba-6 Additional external additive A Silica Surface-treated with HMDS Primary average particle diameter 30nm 30nm H-SiO2 Primary average particle size 3nm 3nm H-SiO2 Primary average particle diameter 60nm 60nm H-SiO2 Untreated Silica Primary average particle diameter 30nm 30nm SiO2 Additional external additive B Silica surface-treated with PDMS Primary Average Particle Diameter 55nm 55nm P-SiO2 Primary average particle diameter 20nm 20nm P-SiO2 Primary Average Particle Diameter 90nm 90nm P-SiO2 Untreated Silica Primary Average Particle Diameter 55nm 55nm SiO2 Additional external additive C Titanium dioxide surface treated with strontium, primary average particle size 80 nm 80 nm St-TiO2 Titanium dioxide surface-treated with strontium, primary average particle size 5nm 5nm St-TiO2 Titanium dioxide surface-treated with strontium, primary average particle size 110nm 110nm St-TiO2 Untreated titanium dioxide, primary average particle size 80 nm 80nm TiO2

Example or Comparative Example Number Barium titanate (addition amount, part by weight) Additional external additive A (addition amount, weight part) Additional external additive B (addition amount, weight part) Additional external additive C (addition amount, weight part) Example 1-1 100nm Ba-1 (2.5) 30nm SiO2 (2.5) 55nm SiO2 (1.5) - Example 1-2 100nm Ba-1 (2.5) 30nm SiO2 (2.5) 55nm SiO2 (1.5) 80 nm TiO2 (1.5) Example 1-3 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) - Example 1-4 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 1-5 100nm Ba-1 (0.2) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 1-6 100nm Ba-1 (7.0) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 1-7 100nm Ba-1 (2.5) 3nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 1-8 100nm Ba-1 (2.5) 60nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 1-9 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 20nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 1-10 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 90nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 1-11 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 5nm St-TiO2 (1.5) Example 1-12 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 110nm St-TiO2 (1.5) Example 1-13 100nm Ba-1 (2.5) 30nm H-SiO2 (6.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 1-14 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (4.5) 80 nm St-TiO2 (1.5) Example 1-15 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (4.5) Comparative Example 1-1 - 30nm SiO2 (2.5) 55nm SiO2 (1.5) 80 nm TiO2 (1.5) Comparative Example 1-2 - 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 1-3 100nm Ba-2 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 1-4 100nm Ba-3 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 1-5 100nm Ba-4 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 1-6 40nm Ba-5 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 1-7 160nm Ba-6 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5)

Example  2-1 to 2-15 and Comparative example  2-1 to 2-8

(Preparation of cyan toner base particles)

Preparation of Latex Particles

400 g of oxygen-free ultrapure water was mixed with 0.5 g of SDS (sodium dodecyl sulfate) as an anionic surfactant to obtain an aqueous solution. The aqueous solution was placed in a reactor and heated to 80 ° C. When the temperature of the aqueous solution reached 80 ° C., an initiator solution in which 0.2 g of potassium persulfate was dissolved in 30 g of ultrapure water was added. After 10 minutes, 105.5 g of styrene, butyl acrylate, and methacrylic acid (81 g, 22 g, 2.5 g, respectively) were added dropwise over about 30 minutes. After reacting for 4 hours, the heating was stopped and naturally cooled to obtain a seed solution. 30 g of the seed solution was mixed with 351 g of ultrapure water, and then heated to 80 ° C. 17 g of ester wax was mixed with 18 g of monomer styrene, 7 g of butyl acrylate, 1.3 g of methacrylic acid, and 0.4 g of dodecanethiol to dissolve by heating. The wax / monomer mixture thus prepared was added to 220 g of ultrapure water in which 1 g of SDS was dissolved, and then homogenized with an ultrasonic disperser for about 10 minutes to obtain a homogenized emulsion. The homogenized emulsified solution was added to the reactor filled with the seed solution, and after about 15 minutes, an initiator solution in which 5 g of an initiator (potassium persulfate) was dissolved in 40 g of ultrapure water was added. At this time, the reaction temperature was maintained at 82 ℃ and the reaction proceeded for 2 hours 30 minutes. After a reaction time of 2 hours 30 minutes, an initiator solution in which 1.5 g of potassium persulfate initiator was dissolved in 60 g of ultrapure water was added, and 56 g of styrene, 20 g of butyl acrylate, and 4.5 g of methacrylic acid were added as monomers for forming a shell layer. , And 3 g of dodecanethiol were added dropwise for about 80 minutes. After 2 hours, the reaction was terminated and naturally cooled to obtain latex particles.

Flocculation / melting process

318 g of the latex particle dispersion thus prepared was mixed with ultrapure water (310 g) in which 0.5 g SDS emulsifier was dissolved. 18.2 g (40 weight% solids) of the pigment particle (Cyan) dispersion liquid disperse | distributed with the SDS emulsifier were mixed here, and the latex pigment dispersion liquid was obtained. Then, the pH of the latex pigment dispersion was titrated to 10 using 10 mol% NaOH buffer while stirring at 250 rpm. To the latex pigment dispersion, a coagulant solution in which 10 g of MgCl _{2 as} a coagulant was dissolved in 30 g of ultrapure water was added dropwise over 10 minutes. Thereafter, the temperature of the mixed solution was raised to 95 ° C at a temperature increase rate of 1 ° C / min. After reacting for 3 hours at the above temperature, the mixture was naturally cooled to obtain toner base particles. The volume average particle diameter of the toner base particles obtained at this time was 6.5 µm.

(External process)

The toner of each example was prepared by treating the untreated toner base particles prepared by the polymerization method with the external additives as shown in Table 3 below, respectively. The external treatment was performed by adding each external additive in Table 3 to the toner base particles (based on 100 parts by weight of the toner base particles) and mixing for 3 minutes with a Henschel type mixer.

Example or Comparative Example Number Barium titanate (addition amount, part by weight) Additional external additive A (addition amount, weight part) Additional external additive B (addition amount, weight part) Additional external additive C (addition amount, weight part) Example 2-1 100nm Ba-1 (2.5) 30nm SiO2 (2.5) 55nm SiO2 (1.5) - Example 2-2 100nm Ba-1 (2.5) 30nm SiO2 (2.5) 55nm SiO2 (1.5) 80 nm TiO2 (1.5) Example 2-3 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) - Example 2-4 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 2-5 100nm Ba-1 (0.2) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 2-6 100nm Ba-1 (7.0) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 2-7 100nm Ba-1 (2.5) 3nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 2-8 100nm Ba-1 (2.5) 60nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 2-9 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 20nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 2-10 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 90nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 2-11 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 5nm St-TiO2 (1.5) Example 2-12 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 110nm St-TiO2 (1.5) Example 2-13 100nm Ba-1 (2.5) 30nm H-SiO2 (6.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Example 2-14 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (4.5) 80 nm St-TiO2 (1.5) Example 2-15 100nm Ba-1 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (4.5) Comparative Example 2-1 - 30nm SiO2 (2.5) 55nm SiO2 (1.5) 80 nm TiO2 (1.5) Comparative Example 2-2 - 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 2-3 100nm Ba-2 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 2-4 100nm Ba-3 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 2-5 100nm Ba-4 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 2-6 40nm Ba-5 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5) Comparative Example 2-7 160nm Ba-6 (2.5) 30nm H-SiO2 (2.5) 55nm P-SiO2 (1.5) 80 nm St-TiO2 (1.5)

<Physical Evaluation Test>

The physical properties of each of the nonmagnetic one-component toners prepared in Examples and Comparative Examples were measured as follows. That is, using a non-magnetic one-component developing printer (HP 4600, Hewlett-Packard Co., Ltd.) equipped with a tandem developing device using color toner, it is 5,000 at constant temperature / humidity (25 ° C / 55% RH). Each sheet was printed and evaluated for image density, charge stability, long-term stability, and charge roller contamination by the following method.

(1) Image density (ID): Solid area images were measured with a Macbeth reflection densitometer SpectroEye, and the results obtained were classified into A, B, C and D grades according to the following criteria:

A: The density of the image is 1.4 or more on average.

B: The density of the images averages 1.3 or more and less than 1.4.

C: The density of the images averages 1.2 or more and less than 1.3

D: The density of the image is 1.2 or less on average.

 (2) Charging stability (%): The charging amount was measured using a Suction Charge Analyzer, and the charging stability was evaluated by comparing with the initial charging amount. The results obtained were then classified into grades A, B, C and D, respectively, according to the following criteria:

A: 95% or more of charging stability.

B: Charging stability 85% or more and less than 95%.

C: Charging stability 75% or more and less than 85%.

D: Charging stability 50% or more and less than 75%.

(If the stability is less than 50%, the image is not printed.)

 (3) Long-term stability: Image density and charging stability were evaluated in the same manner as described above. The results obtained were then classified into grades A, B, C and D, respectively, according to the following criteria:

A: The density of the image is 1.4 or more, and the charging stability is 75% or more.

B: The density of the image is 1.3 or more and less than 1.4, and the charging stability is 70% or more and less than 75%.

C: The density of the image is 1.2 or more and 1.3 or less, and the charging stability is 60% or more and less than 70%.

D: The density of the image is less than 1.2, and the charging stability is 40% or more and less than 60%.

 (4) Whether the roller is dirty

After printing 5,000 sheets, the commercial printer was disassembled and visually observed whether the charging roller mounted thereon was contaminated with toner.

The image density, charge stability, long-term, and contamination of the charging roller measured and observed according to the criteria are shown in Table 4 below.

Example or Comparative Example Number Burn density Charging stability Long-term stability Daejeon Roller Contamination density Rating % Rating Example 1-1 1.42 A 95.1 A A X Example 1-2 1.43 A 95.3 A A X Example 1-3 1.61 A 97.0 A A X Example 1-4 1.80 A 98.4 A A X Example 1-5 1.74 A 98.0 A A X Example 1-6 1.75 A 98.1 A A X Example 1-7 1.77 A 97.5 A A X Example 1-8 1.77 A 97.6 A A X Example 1-9 1.76 A 97.7 A A X Example 1-10 1.77 A 97.6 A A X Example 1-11 1.78 A 97.9 A A X Example 1-12 1.78 A 97.9 A A X Example 1-13 1.77 A 98.0 A A X Example 1-14 1.77 A 98.1 A A X Example 1-15 1.78 A 98.3 A A X Comparative Example 1-1 1.13 D 51.0 D D X Comparative Example 1-2 1.25 C 67.2 C C X Comparative Example 1-3 1.10 B 57.4 C B O Comparative Example 1-4 1.16 B 60.6 D B O Comparative Example 1-5 1.12 B 58.9 D B O Comparative Example 1-6 1.10 D 50.2 D D O Comparative Example 1-7 0.86 D 46.5 D D O Example 2-1 1.42 A 95.1 A A X Example 2-2 1.43 A 95.3 A A X Example 2-3 1.61 A 97.0 A A X Example 2-4 1.80 A 98.4 A A X Example 2-5 1.74 A 98.0 A A X Example 2-6 1.75 A 98.1 A A X Example 2-7 1.77 A 97.5 A A X Example 2-8 1.77 A 97.6 A A X Example 2-9 1.76 A 97.7 A A X Example 2-10 1.77 A 97.6 A A X Example 2-11 1.78 A 97.9 A A X Example 2-12 1.78 A 97.9 A A X Example 2-13 1.77 A 98.0 A A X Example 2-14 1.77 A 98.1 A A X Example 2-15 1.78 A 98.3 A A X Comparative Example 2-1 1.16 D 63.5 D D X Comparative Example 2-2 1.12 C 54.9 C C X Comparative Example 2-3 1.03 B 46.8 C B O Comparative Example 2-4 1.06 B 49.8 B B O Comparative Example 2-5 1.10 B 50.8 B B O Comparative Example 2-6 0.96 D 49.5 D D O Comparative Example 2-7 0.85 D 43.2 D D O

As can be seen in Table 4, when the barium titanate external additive close to the spherical form was used as in the present embodiment, silica of different sizes obtained by surface treatment of the barium titanate external additive with HMDS or PDMS (extra By mixing with additives A and B) and titanium dioxide surface-treated with strontium (additional external additive C), a toner having excellent characteristics in terms of image density, charging stability and long term stability can be prepared. That is, the closer the particle shape is to the spherical shape, the more the particle shape can be maintained even when attached to the toner base particles, and the external additive itself can be reduced when the toners collide with each other as a spacer. In addition, the external additive can be uniformly attached to the toner base particles, thereby improving the charging stability of the toner and not changing the fluidity of the toner. This, in turn, sharpens the charge distribution of the toner so that the toner image can maintain a stable high quality over a long period of time.

Further, while the toner of the comparative example seriously contaminates the charging roller, the toner according to the present embodiment can prevent the charging roller in the developing apparatus from being contaminated.

Although the preferred embodiment according to the present invention has been described above, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the protection scope of the present invention should be defined by the appended claims.

1 is a schematic view showing an example of a main part of an electrophotographic image forming apparatus of a non-contact developing method.

2A is a conceptual diagram showing the distribution of the external additive attached to the surface of the toner base particles when only a spherical external additive is used.

Figure 2b is a conceptual diagram showing the distribution of the external additives attached to the surface of the toner base particles when a mixture of spherical and non-spherical external additives are used.

<Short description of drawing symbols>

1: photosensitive member 2: charging roller

3: exposure signal 4: developing device

5: developing roller 6: feeding roller

7: Toner Doctor Blade 8: Toner

8 ': remaining toner 9: transfer unit

10: cleaning blade 12: power

13: print medium 20: toner base particles

30: external additive

Claims (7)

Toner base particles comprising a binder resin, a colorant, a release agent, and a charge control agent; The primary average particle diameter is 50 to 150 nm, the average shape coefficient SF1 is 100 to 120, the shape factor is 0.96 to 1, and the aspect ratio is 0.89 to 1. Barium Titanate external additive added to the surface; Silica external additive (additional external additive A) having a primary average particle diameter of 5 to 50 nm and surface treated with hexamethyldisilazane (HMDS); And An electrophotographic toner comprising a silica external additive (additional external additive B) having a primary average particle diameter of 30 to 80 nm and surface treated with polydimethylsiloxane (PDMS). The method of claim 1, The barium titanate external additive is included in the ratio of 0.3 to 5 parts by weight based on 100 parts by weight of the toner base particles. delete The method of claim 1, And an inorganic compound having a first average particle diameter of 10 to 100 nm (additional external additive C); as an external additive, And the inorganic compound is selected from silica, titanium compound, alumina, calcium carbonate, magnesium carbonate, calcium phosphate, cesium oxide and barium oxide compound. The method of claim 4, wherein 0.5 to 5 parts by weight of the additional external additive A based on 100 parts by weight of the toner base particles; 0.1 to 3 parts by weight of the additional external additive B; And the additional external additive C in a ratio of 0.1 to 3 parts by weight. The method of claim 1, The toner base particles have an average aspect ratio of 0.975 to 1, and a volume average particle diameter of 5 to 7 µm. An electrophotographic image forming apparatus employing the electrophotographic toner according to any one of claims 1, 2 and 4 to 6.

Images